@redjives@todon.eu I don't keep track of which ones I've read, but if I think I'll want to refer back to a paper I put it in a topic-specific folder in Zotero. I also have folders for papers that I downloaded for specific projects. I usually have few enough papers on a given topic that it doesn't take too long to look through them in the folder to figure out which ones I've read. I sometimes have sub-folders for papers that I *know* I'll want to come back to for specific purposes.